Method and means for remolding hard rubber water-meter disks to precise dimensions



May 6, 1924. 1,492,90

J. THQMSON METHOD AND MEANS FOR REMOLDING HARD RUBBER WATER METER DISKS-TQ PRECISE DIMENS Filed Feb. 24

iNVENTO R:

Patented May 6, 1924.

UNITED STATES PATENT OFFICE.

JOHN THOMSON, OF BROOKLYN, NEW YORK.

METHOD AND MEANS FOR REMOLDING HARD RUBBER WATm-METER DISKS TO 7 PRECISE DIMENSIONS.

Application filed February 24, 1923. Serial No. 620,862.

To all whom it may concern:

Be it known that I, JOHN THOMSON, a citizen of the United States, and a resident of the borough of Brooklyn, city and State of New York, have invented a Method and Means for Remolding Hard Rubber W'ater- MeterDisks to Precise Dimensidns, of which the following is a specification.

This invention relates to water meters, consisting in method and means for remolding hard rubber disks to precise dimensions, used in the construction of water meters; and the objects thereof are to produce such articles. with greater accuracy and smoothness of surface, and at a diminished cost, relative to the prevailing modes of manufacture.

In the disk type of water meter, which now dominates the market, the most diflicult member to produce, thatis within a close plus and minus tolerance of the exact dimensions sought, isthe ball-and-disk used as a nutatingpiston but popularly referred to under the unitary term disk. That the many attempts to vulcanize rubber in steel molds and thereby turn out a fully or nearly finished disk have not been satisfactory is well attested by the fact that the hundreds of thousands of them now being made annually are machined from rough-stock, usually by diamond-pointed tools, or by grinding, or both. The present applicant formerly endeavored to mold disks directfrom-the-crude, and also to remold, them from pro-vulcanized disks, but such success as was attained did not meet technical and commercial requirements and further research was then abandoned.

With respect to hard rubber per se, the state of the art is so well known that a present recitation thereof would seem to be supererogatory; but it may serve to more readily visualize the ensuing subject-matter to briefly state that, when so confined as to prevent displacement, rubber is about as irresponsive to compressive deformation as water. When heated, say from about 225 to 300 F., de ending upon its compounding, hard rub er becomes plastic, when it may be likened to molten sealin -wax, or bitumen, or the pasty condition 0 wrought iron at its welding temperature. In fact, it then simulates a fluid; which, however, is

characterized by possessing an abnormally high viscosity. Again, if brought into conmolded article with a sprue whose volume is about equal to or exceeds that of the mass necessary to impart to the said rou h-molded article and swell it to the desire dimensions of the finished part; to place the said rough molded article and its sprue in a separable molding die of precise dimensions and firmly clamped together; to heat the said die and the article therein contained to some pro-determined temperature; to a ply pressure to the said sprue, causing it to sow, as a fluid, dis lacively into the article, thereby completely lling the die-cavity; and to then 0001 the die with its contained finished part, the pressure primarily imparted being meantime maintained.

Means for realizing the foregoing methods are shown in the accompanying drawings, which form a part of this specification, wherein- Figure 1 is'a transverse center section of a finlshing die, or mold, in which a roughmolded under-sized disk and sprue are shown in elevation; ddlligure 2 is a plan view of the finished gigure 3 is a revolved elevai'on thereof; an

Figure 4 is a com osite transverse section showing so-called isks of various forms.

This finishing die is comprised in a cylinder 5 having an underlying flange 6 and upper lugs, as 7, in which is contained a lower plug 8 resting on the said flange and an upper plug 9 having lugs, as 10, resting upon the upper cylinder-face 11.

The inner faces of the saidplugs are machined, with the utmost accuracy, so that when the lugs are firmly secured together, as by headed lDltS and nuts 13, 14, the cavity of the desired disk.

The upper plu is bored, as 15, to receive the sprue A whic rises from the ball B of will precisely correspond to that of the form Y dimensions of the disk and its sprue should preferably be such that it will drop freely into piace, leaving a clear space around it, permitting the plugs to be very 'firmlyclamped. together without imparting pressure to the cold and solid hard rubber. The

aforesaid condition is shown in Figure 1, to

.a somewhat exaggerated scale, the center of the disk-ball being preferably caused to coil'icidewith-thecenter of the sockets, as by means of a tit 20.

According to the foregoing, the ensuing steps for realizing the method may now be taken. Thus, heat the die and its contained rough-molded disk; turn down the plunger, causing the sprue tofiow into and displace the underlying mastic-like mass until the diespace is absolutely filled; finally, cool the die and its contained finished article. Then by unclamping the lug-bolts and pushing the plugs out from the cylinder, upwardly, they can be readily se arated and the disk be removed without deibrming it.

As the rough-molding operation cannot'be performed within close dimension tolerances, that is without unduly increasing the cost thereof, it is preferable. to form the sprue of such ample volume that the longer cannot be forced down into the ball ut will stop, as at the dotted line (i, leaving a boss, as 21, Figure 3, to be removed by machining. Therefore, this boss will vary in height from one to another according to the dimensions of premolded disks;

It is of prime importance to -fulfill the concept of this method that the air-all of it-oontained in the free space'surrounding the pro-molded disk shall be expelled; for if imprisoned, or if pocketed in different parts of the die, precise dimensions will not and cannot be imparted to the finished part. This feature is here readily realized by forming theperimeters of the plugs, contiguous to their inner faces, to

slightly lesser diameters than that of the lower and u per centering .perimeters, as denoted by t e heavy lines 22, 23, and to these circular recesses-. (a diminution in their diameters of, say, .004 inch is suflicient) one or more shallow connecting ventsare provided, as 24, 25, reaching to atmos' phere. Thus, the incipient apphcatlon of pressure upon the sprue effects the followmg results, namely: The upper and lower parts of the ball are bulged outwardly to the socket surfaces; as the inward flow of the s rue continues, air around the ball is .roll out to the disc-spaces; and, as these naeaeoe disc-spaces contiguous to the sockets be-' It will be manifest that, as the cross-sectional area of the plunger is many times less than that of the face-area of the plugs, the amount of pressure readily impartable to the mastic rubber is such as ma be lim-v ited only by the rigidity of the ug-bolts;-

that all portions of the finished part are uniform in density; and that the surfaces of the completed disk are as smooth, or polished, as may be the acting surfaces of the d ie-plugs. Moreover, subsequent gauging may be largely dispensed with; for the die itself functions as a gauge.

The manufacturing maneuver is both simple, expeditious and inexpensive; for, given a plurality of dies, it is resolved into a circulating chain: (a); fill and clamp a die; (7)) pass it to a heating chamber; withdraw and compress; ((1) set aside and cool; (e) remove the finished part, and so on interminably.

A contingent feature of singular commercial importance is that the method and means hereof may be most advanta eously applied to the production of disks lor the larger sizes'of water meters; which, so far as this applicant is now aware, has not even been contemplated in connection with the systems of finish-molding hitherto attem ted.

arious modifications can readily be made inthe means here depicted and described. For example, the plunger need not revolve upon the head of the sprue but may act against an interposed washer. Pressure may be applied hydraulicallypr by compressed air. If one desires, the disk-slot, denoted in dotted outline 26, Figure 2. may well be molded, as is also the case if a in-bearing, through the ball, is wanted, enoted by dotted outline 27. A ain, the sprue may be applied right and le t, as A and C, Figurefi, when both theplugs would be provided with pressureplungers, to be simultaneously operated and thereby cause two opposing streams of plastic rubber to flow inwardly, one against the other of them.

Whilst the means depicted in the drawing and correspondingly described are adapts for producing a water meter d1Sk, 'Vl:l110l1 1s probably the most diflicult exhib t that could be selected, the general principles of construction and operation are readily apaaaaeoe plicable to various other parts used in water meters, such as turbines, gears and pinions; and also to parts for other purposes.

Where the unitary term disk is herein employed it is to be understood as-in inclusive rather than a restrictive expression. For example, any one of the three forms shown in Figure 4:, as h, m, n, the latter simulating a conical cup with a ball at its apex, each being difl'erent from that shown in the preceding figures, is now properly designatable in the water meter art as a disk. I In fact, the outwardly tapering section, m, would doubtless have been the predominating form but for the greater difficulty in machining and gaugin it. If die lgglded, it can be as readily pro need as if its faces are parallel.

What I claim is:

l. The method of remolding a hard rubber disk to precise dimensions which consists in re-forming it to less'than the required nished dimensions and providing it with a sprue, the combined volumes thereof being approximatel equal to or greater than the volume of t e finished disk; inserting the said pre-formed under-sized disk and sprue in a separable molding die and clamping said die together; heating them to a temperature at which hard rubber becomes plastic and flowable; applying rubber pro-formed disk having a sprue thereon, of less dimensions than the diespaces; and an actuatable plunger mounted in the die and adapted to impose pressure upon the head of said sprue; whereby, when the pro-formed disk and its sprue are heated to a state of plasticity, they are caused to flow and completely fill the die-cavity.

3. In water meters, as a co-ordinating element in the means for realizing the method hereof, a roughly-formed undersize disk having an integral sprue, the volume of said sprue being approximately equal to or greater than the volume necessarily impartable to the disk, whereb its dimensions can be increased to that c the die-cavity.

4. In water meters and according to the method and means hereof, a disk die-molded when plastic to precise dimensions from a pie-formed hard rubber disk of less dimensions than the finished disk.

This specification signed on this the 22d day of February, A. D. 1923.

JOHN THOMSON, 

